Is FENO50 useful diagnostic tool in suspected asthma?

Development and validation of a predictive model combining patient-reported outcome measures, spirometry and exhaled nitric oxide fraction for asthma diagnosis

Introduction

Although asthma is a common disease, its diagnosis remains a challenge in clinical practice with both over- and underdiagnosis. Here, we performed a prospective observational study investigating the value of symptom intensity scales alone or combined with spirometry and exhaled nitric oxide fraction (F _ENO) to aid in asthma diagnosis.

Methods

Over a 38-month period we recruited 303 untreated patients complaining of symptoms suggestive of asthma (wheezing, dyspnoea, cough, sputum production and chest tightness). The whole cohort was split into a training cohort (n=166) for patients recruited during odd months and a validation cohort (n=137) for patients recruited during even months. Asthma was diagnosed either by a positive reversibility test (≥12% and ≥200 mL in forced expiratory volume in 1 s (FEV₁)) and/or a positive bronchial challenge test (provocative concentration of methacholine causing a 20% fall in FEV₁ ≤8 mg·mL^-1). In order to assess the diagnostic performance of symptoms, spirometric indices and F _ENO, we performed receiver operating characteristic curve analysis and multivariable logistic regression to identify the independent factors associated with asthma in the training cohort. Then, the derived predictive models were applied to the validation cohort.

Results

63% of patients in the derivation cohort and 58% of patients in the validation cohort were diagnosed as being asthmatic. After logistic regression, wheezing was the only symptom to be significantly associated with asthma. Similarly, FEV₁ (% pred), FEV₁/forced vital capacity (%) and F _ENO were significantly associated with asthma. A predictive model combining these four parameters yielded an area under the curve of 0.76 (95% CI 0.66-0.84) in the training cohort and 0.73 (95% CI 0.65-0.82) when applied to the validation cohort.

Conclusion

Combining a wheezing intensity scale with spirometry and F _ENO may help in improving asthma diagnosis accuracy in clinical practice.

European Respiratory Society Guidelines for the Diagnosis of Asthma in Adults

Although asthma is very common affecting 5-10% of the population, the diagnosis of asthma in adults remains a challenge in the real world that results in both over- and under-diagnosis. A task force (TF) was set up by the European Respiratory Society to systematically review the literature on the diagnostic accuracy of tests used to diagnose asthma in adult patients and provide recommendation for clinical practice.The TF defined eight PICO (Population, Index, Comparator, and Outcome) questions that were assessed using the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach, The TF utilised the outcomes to develop an evidenced-based diagnostic algorithm, with recommendations for a pragmatic guideline for everyday practice that was directed by real-life patient experiences.The TF support the initial use of spirometry followed, and if airway obstruction is present, by bronchodilator reversibility testing. If initial spirometry fails to show obstruction, further tests should be performed in the following order: FeNO, PEF variability or in secondary care, bronchial challenge. We present the thresholds for each test that are compatible with a diagnosis of asthma in the presence of current symptoms.The TF reinforce the priority to undertake spirometry and recognise the value of measuring blood eosinophils and serum IgE to phenotype the patient. Measuring gas trapping by body plethysmography in patients with preserved FEV1/FVC ratio deserves further attention. The TF draw attention on the difficulty of making a correct diagnosis in patients already receiving inhaled corticosteroids, the comorbidities that may obscure the diagnosis, the importance of phenotyping, and the necessity to consider the patient experience in the diagnostic process.

Blood eosinophils, FeNO and small airways dysfunction in predicting airway hyperresponsiveness in patients with asthma-like symptoms

PURPOSE

In patients with suspected asthma and no airflow limitation in spirometry, methacholine challenge testing (MCT) for airway hyperresponsiveness (AHR) is an option of documenting variable airflow limitation. The goal of the study was to assess the ability of blood eosinophils, fractional concentration of exhaled nitric oxide (FeNO) and distal airways function to discriminate patients with AHR from those with normal airway responsiveness (AR).

METHODS

We analyzed baseline data from 42 participants who underwent MCT because of asthma-like symptoms and no airflow limitation in spirometry.

RESULTS

Eosinophil count was higher among participants with borderline AHR comparing to those with normal AR (340 cells/µL, IQR 285-995 vs. 125 cells/µL, IQR 75-180, post-hoc p = 0.041). FeNO and percent predicted of functional residual volume (FRC%pred) were higher in participants with moderate-marked AHR compared to those with normal AR (40 ppb, IQR 30.5-100.5 vs. 18 ppb, IQR 13-50, post-hoc p = 0.008; 140.1%±17.0% vs. 107.3%±20.7%, post-hoc p < 0.001, respectively). Percentage predicted of the maximal expiratory flow at 25% of the forced vital capacity (MEF₂₅%pred) was lower in participants with mild AHR and borderline AHR compared to those with normal AR (72.9%±16.9% vs. 113.0%±36.8%, post-hoc p = 0.017; 73.3%±15.9% vs. 113.0%±36.8%, post-hoc p = 0.045; respectively). Level of AHR correlated with eosinophil count, FeNO, MEF₂₅%pred, forced expiratory flow between 25% and 75% of vital capacity (FEF_25-75%pred), FRC%pred and specific airway resistance (sR_aw).

CONCLUSIONS

Blood eosinophils, FeNO and small airways dysfunction markers are related to the level of AR to methacholine in patients with asthma-like symptoms and no airflow limitation in spirometry.

Small-Airway Function Variables in Spirometry, Fractional Exhaled Nitric Oxide, and Circulating Eosinophils Predicted Airway Hyperresponsiveness in Patients with Mild Asthma

Purpose

Patients with variable symptoms suggestive of asthma but with normal forced expiratory volume in 1 second (FEV₁) often fail to be diagnosed without a bronchial provocation test, but the test is expensive, time-consuming, risky, and not readily available in all clinical settings.

Patients and Methods

A cross-sectional study was performed in 692 patients with FEV₁≥80% predicted; normal neutrophils and chest high-resolution computed tomography; and recurrent dyspnea, cough, wheeze, and chest tightness.

Results

Compared with subjects negative for AHR (n=522), subjects positive for AHR (n=170) showed increased FENO values, peripheral eosinophils (EOS), and R5-R20; decreased FEV₁, FEV₁/Forced vital capacity (FVC), and forced expiratory flow (FEFs) (P≤.001 for all). Small-airway dysfunction was identified in 104 AHR⁺ patients (61.17%), and 132 AHR⁻ patients (25.29%) (P<0.001). The areas under the curve (AUCs) of variables used singly for an AHR diagnosis were lower than 0.77. Using joint models of FEF_50%, FEF_75%, or FEF_25%-75% with FENO increased the AUCs to 0.845, 0.824, and 0.844, respectively, significantly higher than univariate AUCs (P <0.001 for all). Patients who reported chest tightness (n=75) had lower FEFs than patients who did not (P<0.001 for all). In subjects with chest tightness, the combination of FEF_50% or FEF_25%-75% with EOS also increased the AUCs substantially, to 0.815 and 0.816, respectively (P <0.001 for all versus the univariate AUCs).

Conclusion

FENO combined with FEF_50% and FEF_25%-75% predict AHR in patients with normal FEV₁. FEF_25%-75%, FEF_50%, or FEF_25%-75% together with EOS also can potentially suggest asthma in patients with chest tightness.

Predictive Markers of Bronchial Hyperreactivity in a Large Cohort of Young Adults With Cough Variant Asthma

Cough variant asthma (CVA), a common asthma phenotype characterized by nonproductive cough and bronchial hyperreactivity (BHR), is usually detected by bronchial provocation tests (BPTs) which are time-consuming, expensive, and unsafe. The primary study objective was to provide proof of concept for the use of fractional exhaled nitric oxide (F_ENO), eosinophil count percentage in induced sputum (sEOS%), forced expiratory flow between 25 and 75% of forced vital capacity (FEF_25–75%) % predicted value, and FEF_25–75% z-scores as surrogate markers predicting BHR in young adults with suspected CVA; the secondary objective was to compare the diagnostic performance of the various techniques. Three hundred and ten subjects (median age 24 years) were included in a cross-sectional study. Subjects were characterized as BHR positive (POS) (n = 147) or BHR negative (NEG) (n = 163) according to methacholine BPT. Classification accuracies were expressed as areas under the receiver operator characteristic curves (AUC). Compared with BHR NEG, FEF_25–75% % predicted value and FEF_25–75% z-scores were lower in the BHR POS group (p < 0.001), whereas F_ENO (p < 0.001) and sEOS% were higher (p < 0.001). AUC values for detecting BHR were as follows: F_ENO, 0.98 (SD = 0.02); sEOS%, 0.98 (SD = 0.02); FEF_25–75% % pred, 0.93 (SD = 0.05); FEF_25–75% z scores, 0.92 (SD = 0.05). Optimal cutoff values (OCV) for BHR prediction were as follows: F_ENO, 32.7 ppb (sensitivity = 0.93, specificity = 0.96), sEOS%, 3.80% (sensitivity = 0.94, specificity = 0.94), FEF_25–75% % predicted value, 80.0% (sensitivity = 0.90, specificity = 0.87), and FEF_25–75% z-score, −0.87 (sensitivity = 0.89, specificity = 0.87). Non-invasive/semi-invasive airway inflammatory or small airway functional measures might be used as surrogate markers predicting BHR in young adults with suspected CVA.

The value of small airway function parameters and fractional exhaled nitric oxide for predicting positive methacholine challenge test in asthmatics of different ages with FEV1 ≥ 80% predicted

Background

Small airway function parameters (SAFPs) combined with fractional exhaled nitric oxide (FeNO) can predict a positive methacholine challenge test (MCT) for asthma diagnosis. However, their predictive utility in patients with forced expiratory volume in one second (FEV₁) ≥80% predicted within different age ranges remains unclear. This study aimed to assess the utility of SAFPs, alone or combined with FeNO, to predict a positive MCT in patients in two age groups (<55 and ≥55 years) with asthma‐suggestive symptoms and FEV₁ ≥80% predicted.

Methods

We enrolled 846 Chinese patients with suspected asthma and standard spirometry, FeNO, and MCT findings. Using the area under the curves (AUCs), the utility of SAFPs, alone or combined with FeNO, for predicting a positive MCT was analyzed in a discovery (n = 534) and validation cohort (n = 312) in both age groups with FEV₁ ≥80% predicted.

Results

In the discovery cohort, the optimal cut‐off values for predicting a positive MCT in patients aged <55 years (74.2% and 74.9% for forced expiratory flow (FEF)_50% and FEF_25%–75%, respectively) were higher than those in patients aged ≥55 years (65.0% and 62.9% for FEF_50%, FEF_25%–75%, respectively). However, the optimal FeNO value in patients aged <55 years (43 ppb) was lower than that in patients aged ≥55 years (48 ppb). FeNO combined with SAFPs (FEF_50%, FEF_25%–75%) significantly increased the AUCs in both groups (≥55 years [0.851 for FEF_50% and 0.844 for FEF_25%–75%]; <55 years [0.865 for FEF_50% and 0.883 for FEF_25%–75%]) compared with a single parameter (p < 0.05). These findings were confirmed in the validation cohort. Compared with patients ≥55 years, those aged <55 years had higher and lower optimal cut‐off values for SAFPs and FeNO, respectively. The AUCs of FeNO combined with SAFPs for predicting a positive MCT for asthma diagnosis were significantly higher than those of the individual parameters (p < 0.05) in both age groups.

Conclusions

There were age‐group differences in the utility of SAFPs combined with FeNO for predicting a positive MCT. Patients with an asthma‐suggestive history and a normal FEV₁ should be stratified by age when using SAFPs combined with FeNO to predict a positive MCT.

Assessment of diagnostic accuracy of lung function indices and FeNO for a positive methacholine challenge

Demonstration of bronchial hyperresponsiveness is a key feature in asthma diagnosis. Methacholine challenge has proved to be a highly sensitive test to diagnose asthma in patients with chronic respiratory symptoms and preserved baseline lung function (FEV1 > 70% pred.) but is time consuming and may sometimes reveal unpleasant to the patient. We conducted a retrospective study on 270 patients recruited from the University Asthma Clinic of Liege. We have compared the values of several lung function indices and fractional exhaled nitric oxide (FeNO) in predicting a provocative methacholine concentration ≤16 mg/ml on a discovery cohort of 129 patients (57 already on ICS) and on a validation cohort of 141 patients (66 already on ICS). In the discovery study (n = 129), 85 patients (66%) had a positive methacholine challenge with PC20M ≤ 16 mg/ml. Those patients had lower baseline % predicted FEV1 (92% vs. 100%; p < 0.01), lower FEV1/FVC ratio (79% vs. 82%; p < 0.05), higher RV/TLC ratio (114% vs. 100%; p < 0,0001), lower SGaw (specific conductance) (0.76 vs. 0.95; p < 0,001) and higher FeNO (29 ppb vs. 19 ppb; p < 0,01). When performing ROC curve the RV/TLC ratio provided the greatest AUC (0.74, p < 0.001), sGAW had intermediate AUC of 0.69 (p < 0.001) while FeNO, FEV1 and FEV1/FVC ratio were modestly predictive (AUC of 0.65 (p < 0.05), 0,67 (p < 0.001) and 0,63 (p < 0.001). These results were confirmed in the validation study (n = 141). Based on a logistic regression analysis, significant variables associated with positive methacholine challenge were FeNO and RV/TLC (% Pred). A combined application of FeNO and RV/TLC (% Pred) for predicting the PC20M had a specificity of 85%, a sensitivity of 59% and an AUC of 0.79. In the validation study, three variables (RV/TLC, FeNO and FEV1) were independently associated with positive methacholine challenge and the combination of these three variables yielded a specificity of 77%, a sensitivity of 39% and an AUC of 0.77. The RV/TLC ratio combined to FeNO may be of interest to predict significant methacholine bronchial hyperresponsiveness.

Priorities for future research into asthma diagnostic tools: A PAN-EU consensus exercise from the European asthma research innovation partnership (EARIP)

The diagnosis of asthma is currently based on clinical history, physical examination and lung function, and to date, there are no accurate objective tests either to confirm the diagnosis or to discriminate between different types of asthma. This consensus exercise reviews the state of the art in asthma diagnosis to identify opportunities for future investment based on the likelihood of their successful development, potential for widespread adoption and their perceived impact on asthma patients. Using a two-stage e-Delphi process and a summarizing workshop, a group of European asthma experts including health professionals, researchers, people with asthma and industry representatives ranked the potential impact of research investment in each technique or tool for asthma diagnosis and monitoring. After a systematic review of the literature, 21 statements were extracted and were subject of the two-stage Delphi process. Eleven statements were scored 3 or more and were further discussed and ranked in a face-to-face workshop. The three most important diagnostic/predictive tools ranked were as follows: "New biological markers of asthma (eg genomics, proteomics and metabolomics) as a tool for diagnosis and/or monitoring," "Prediction of future asthma in preschool children with reasonable accuracy" and "Tools to measure volatile organic compounds (VOCs) in exhaled breath."

Clinical utility of ultrahigh fractional exhaled nitric oxide in predicting bronchial hyperresponsiveness in patients with suspected asthma

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is a non-invasive biomarker for airway eosinophilic inflammation. However, the clinical value of ultrahigh FeNO (≥100 parts per billion (ppb)) in predicting asthma is never explored. We aimed to investigate the value of ultrahigh FeNO as a predictor of bronchial hyperresponsiveness (BHR), an important index for asthma diagnosis.

METHODS

A retrospective cohort study was conducted on 259 patients with suspected asthma who received the examination of FeNO, spirometry, bronchial provocation test (BPT) and differential cell count of induced sputum. Patients were stratified by FeNO value: ultrahigh (group A:≥100 ppb), high (group B: 50-99 ppb), intermediate (group C: 26-49 ppb) and normal (group D:≤25 ppb). The positive rates of BPT and sputum eosinophils percentage (Eos%) were compared among four cohorts. The correlations between FeNO and sputum Eos% were measured.

RESULTS

A significant higher positive rate of BPT was observed in group A (90.91%) than all others (B: 51.43%, C: 31.43%, D: 28.13%, all p<0.01). Referring to group D, the ORs of positive BPT in groups A, B and C were 26.84, 2.84 and 1.05. Sputum Eos% in group A (19.75 (7.00, 46.25)) is higher than that in others (B: 3.50 (1.00, 12.75), C: 1.13 (0.06,3.50), D: 0.50 (0.00, 2.13)). FeNO correlates with sputum Eos% in groups A and B, but not group C or D.

CONCLUSIONS

Ultrahigh FeNO correlates with BHR and could serve as a practical alternative to methacholine challenge to support an asthma diagnosis in patients with suspected asthma in primary care.

Accuracy of objective tests for diagnosing adult asthma in symptomatic patients: A systematic literature review and hierarchical Bayesian latent-class meta-analysis

BACKGROUND

We obtain summary estimates of the accuracy of additional objective tests for the diagnosis of adult asthma using systematic review and meta-analysis of diagnostic test accuracy studies.

METHODS

Medline, Embase, and other relevant electronic databases were searched for papers published between January 1989 and December 2016. Studies were included if they evaluated the diagnostic accuracy of objective tests, including airway reversibility (AR), airway hyperresponsiveness (AHR), and fractionated exhaled nitric oxide (FeNO) for the diagnosis of adult asthma in patients with symptoms suggestive of asthma. If papers were assessed appropriate using the adapted QUADAS-2 tool, meta-analysis was conducted using the hierarchical bivariate model. This hierarchical model accounts for both within and between study variability.

RESULTS

Sixteen studies reported the performance of the evaluated objective tests at presentation. For diagnosis of adult asthma, overall sensitivity and specificity for AR were 0.39 (95% confidence interval [CI] 0.18 to 0.66) and 0.95 (95% CI 0.86 to 1.00); for AHR, 0.86 (95% CI 0.61 to 1.00) and 0.95 (95% CI 0.77 to 1.00); for FeNO, 0.65 (95% CI 0.53 to 0.77) and 0.83 (95% CI 0.75 to 0.90). Comprehensive comparison of three diagnostic tools for adult asthma using the back-calculated likelihood rate (LR) showed that AR and AHR corresponded to a higher LR+, and AHR gave a lower LR-.

CONCLUSIONS

In the current situation of no gold standard for diagnosis of adult asthma, AR and AHR are appropriate for ruling-in the true diagnosis, and AHR is superior for ruling-out a diagnosis. Since each objective test had a specific characteristic, it should be chosen depending on the situation, such as the capacity of the institution and the conditions of patients.

The Value of Fractional Exhaled Nitric Oxide and Forced Mid-Expiratory Flow as Predictive Markers of Bronchial Hyperresponsiveness in Adults with Chronic Cough

BACKGROUND

Bronchial provocation tests are standard for diagnosing the etiology of chronic cough, but they are time consuming and can induce severe bronchospasm. A safer and faster clinical examination to predict bronchial hyperresponsiveness (BHR) is needed.

OBJECTIVE

The objective of this study was to investigate whether small-airway function tests can predict BHR in adult patients with chronic cough.

METHODS

A retrospective, cross-sectional study of diagnoses made using spirometry and bronchial provocation test results was performed in 290 patients with chronic nonproductive cough. BHR-predictive values were analyzed via the area under receiver operating characteristic curves (AUCs). Optimal cutoff values were determined by maximizing the sum of sensitivity and specificity.

RESULTS

Patients with chronic cough with BHR showed lower forced expiratory flow between 25% and 75% (FEF_25%-75%), higher fractional exhaled nitric oxide (FENO), and a higher percentage of eosinophils in blood than patients without BHR (P < .0001 for all). The AUCs of FENO and FEF_25%-75% for a BHR diagnosis were 0.788 (95% CI, 0.725-0.851) and 0.702 (95% CI, 0.641-0.763), respectively. Optimal cutoff values were 43 ppb for FENO and 78.5% for FEF_25%-75%, with negative predictive values of 85.38% and 81.34%, respectively. The combined use of FENO and FEF_25%-75% increased the AUC to 0.843 (95% CI, 0.794-0.892), significantly higher than either FENO (P = .012) or FEF_25%-75% (P < .0001) alone.

CONCLUSIONS

Small-airway dysfunction is present in patients with chronic cough and BHR. FEF_25%-75% has value as a negative predictive parameter for BHR, especially when combined with FENO. FENO > 43 ppb and FEF_25%-75% < 78.5% strongly predicted a positive bronchial provocation test.

A novel statistical model for analyzing data of a systematic review generates optimal cutoff values for fractional exhaled nitric oxide for asthma diagnosis

OBJECTIVES

Measurement of fractional exhaled nitric oxide (FE_NO) might substitute bronchial provocation for diagnosing asthma. However, optimal FE_NO thresholds for diagnosing asthma remain unclear. We reanalyzed data collected for a systematic review investigating the diagnostic accuracy of FE_NO measurement to exploit all available thresholds under consideration of pretest probabilities using a newly developed statistical model.

STUDY DESIGN AND SETTING

One hundred and fifty data sets for a total of 53 different cutoffs extracted from 26 studies with 4,518 participants were analyzed with the multiple thresholds model. This model allows identifying thresholds at which the test is likely to perform best.

RESULTS

Diagnosing asthma might only be possible in a meaningful manner when the pretest probability of asthma is at least 30%. In that case, FE_NO > 50 ppb leads to a positive predictive value of 0.76 [95% confidence interval (CI): 0.29-0.96]. Excluding asthma might only be possible, when the pretest probability of asthma is 30% at maximum. Then, FE_NO < 20 ppb leads to a negative predictive value of 0.86 (95% CI 0.66-0.95).

CONCLUSION

The multiple thresholds model generates a more comprehensive and more clinically useful picture of the effects of different thresholds, which facilitates the determination of optimal thresholds for diagnosing or excluding asthma with FE_NO measurement.

Exhaled nitric oxide in the diagnosis of asthma in adults: a systematic review

OBJECTIVES

To identify and synthesize evidence on the diagnostic accuracy of _FE NO for asthma in adults.

MATERIALS AND METHODS

Systematic searches (nine key biomedical databases and trial registers) were carried out on November 2014. Records were included if they recruited patients with the symptoms of asthma; used a single set of inclusion criteria; measured _FE NO₅₀ in accordance with American Thoracic Society guidelines, 2005 (off-line excluded); reported/allowed calculation of true-positive, true-negative, false-positive and false-negative patients as classified against any reference standard. Study quality was assessed using QUADAS II. Meta-analysis was planned where clinical study heterogeneity allowed. Rule-in and rule-out uses of _FE NO were considered.

RESULTS

A total of 4861 records were identified originally and 1312 in an update. Twenty-seven studies were included. Heterogeneity precluded meta-analysis. Results varied even within subgroups of studies. Cut-off values for the best sum of sensitivity and specificity varied from 12 to 55 p.p.b., but did not produce high accuracy. 100% sensitivity or 100% specificity was reported by some studies indicating potential use as a rule-in or rule-out strategy.

CONCLUSIONS AND CLINICAL RELEVANCE

_FE NO₅₀ had variable diagnostic accuracy even within subgroups of studies with similar characteristics. Diagnostic accuracy, optimal cut-off values and best position for _FE NO₅₀ within a pathway remain poorly evidenced.

Accuracy of FENO for diagnosing asthma: a systematic review

BACKGROUND

Measurement of FE_NO might substitute bronchial provocation for diagnosing asthma. We aimed to investigate the diagnostic accuracy of FE_NO measurement compared with established reference standard.

METHODS

Systematic review and diagnostic meta-analysis. Data sources were Medline, Embase and Scopus up to 29 November 2015. Sensitivity and specificity were estimated using a bivariate model. Additionally, summary receiver-operating characteristic curves were estimated.

RESULTS

26 studies with 4518 participants (median 113) were included. Risk of bias was considered low for six of seven items in five studies and for five items in seven studies. The overall sensitivity in the meta-analysis was 0.65 (95% CI 0.58 to 0.72), the overall specificity 0.82 (0.76 to 0.86), the diagnostic OR 9.23 (6.55 to 13.01) and the area under the curve 0.80 (0.77 to 0.85). In meta-regression analyses, higher cut-off values were associated with increasing specificity (OR 1.46 per 10 ppb increase in cut-off) while there was no association with sensitivity. Sensitivities varied significantly within the different FE_NO devices, but not specificities. Neither prevalence, age, use of bronchoprovocation in >90% of participants or as exclusive reference standard test, nor risk of bias were significantly associated with diagnostic accuracy.

CONCLUSIONS

There appears to be a fair accuracy of FE_NO for making the diagnosis of asthma. The overall specificity was higher than sensitivity, which indicates a higher diagnostic potential for ruling in than for ruling out the diagnosis of asthma.

Measurement of exhaled nitric oxide concentration in asthma: a systematic review and economic evaluation of NIOX MINO, NIOX VERO and NObreath

BACKGROUND

High fractions of exhaled nitric oxide (FeNO) in the breath of patients with symptoms of asthma are correlated with high levels of eosinophils and indicate that a patient is likely to respond to inhaled corticosteroids. This may have a role in the diagnosis and management of asthma.

OBJECTIVE

To assess the diagnostic accuracy, clinical effectiveness and cost-effectiveness of the hand-held electrochemical devices NIOX MINO(®) (Aerocrine, Solna, Sweden), NIOX VERO(®) (Aerocrine) and NObreath(®) (Bedfont Scientific, Maidstone, UK) for the diagnosis and management of asthma.

DATA SOURCES

Systematic searches were carried out between March 2013 and April 2013 from database inception. Databases searched included MEDLINE, EMBASE, the Cochrane Database of Systematic Reviews, the Database of Abstracts of Reviews of Effects, Science Citation Index Expanded and Conference Proceedings Citation Index - Science. Trial registers such as ClinicalTrials.gov and the metaRegister of Controlled Trials were also searched in March 2013. All searches were updated in September 2013.

REVIEW METHODS

A rapid review was conducted to assess the equivalence of hand-held and chemiluminescent FeNO monitors. Systematic reviews of diagnostic accuracy and management efficacy were conducted. A systematic review of economic analyses was also conducted and two de novo health economic models were developed. All three reviews were undertaken according to robust high-quality methodology.

RESULTS

The rapid review (27 studies) found varying levels of agreement between monitors (Bland-Altman 95% limits of agreement up to ±10 parts per billion), with better agreement at lower FeNO values. Correlation was good (generally r > 0.9). The diagnostic accuracy review identified 22 studies in adults (all ages) and four in children. No studies used NObreath or NIOX VERO and seven used NIOX MINO. Estimates of diagnostic accuracy varied widely. FeNO used in combination with another test altered diagnostic accuracy only slightly. High levels of heterogeneity precluded meta-analysis. Limited observations included that FeNO may be more reliable and useful as a rule-in than as a rule-out test; lower cut-off values in children and in smokers may be appropriate; and FeNO may be less reliable in the elderly. The management review identified five randomised controlled trials in adults, one in pregnant asthmatics and seven in children. Despite clinical heterogeneity, exacerbation rates were lower in all studies but not generally statistically significantly so. Effects on inhaled corticosteroid (ICS) use were inconsistent, possibly because of differences in management protocols, differential effectiveness in adults and children and differences in population severity. One UK diagnostic model and one management model were identified. Aerocrine also submitted diagnostic and management models. All had significant limitations including short time horizons and the selective use of efficacy evidence. The de novo diagnostic model suggested that the expected difference in quality-adjusted life-year (QALY) gains between diagnostic options is likely to be very small. Airway hyper-responsiveness by methacholine challenge test is expected to produce the greatest QALY gain but with an expected incremental cost-effectiveness ratio (ICER) compared with FeNO (NObreath) in combination with bronchodilator reversibility of £1.125M per QALY gained. All remaining options are expected to be dominated. The de novo management model indicates that the ICER of guidelines plus FeNO monitoring using NObreath compared with guidelines alone in children is expected to be approximately £45,200 per QALY gained. Within the adult subgroup, FeNO monitoring using NObreath compared with guidelines alone is expected to have an ICER of approximately £2100 per QALY gained. The results are particularly sensitive to assumptions regarding changes in ICS use over time, the number of nurse visits for FeNO monitoring and duration of effect.

CONCLUSIONS

Limitations of the evidence base impose considerable uncertainty on all analyses. Equivalence of devices was assumed but not assured. Evidence for diagnosis is difficult to interpret in the context of inserting FeNO monitoring into a diagnostic pathway. Evidence for management is also inconclusive, but largely consistent with FeNO monitoring resulting in fewer exacerbations, with a small or zero reduction in ICS use in adults and a possible increased ICS use in children or patients with more severe asthma. It is unclear which specific management protocol is likely to be most effective. The economic analysis indicates that FeNO monitoring could have value in diagnostic and management settings. The diagnostic model indicates that FeNO monitoring plus bronchodilator reversibility dominates many other diagnostic tests. FeNO-guided management has the potential to be cost-effective, although this is largely dependent on the duration of effect. The conclusions drawn from both models require strong technical value judgements with respect to several aspects of the decision problem in which little or no empirical evidence exists. There are many potential directions for further work, including investigations into which management protocol is best and long-term follow-up in both diagnosis and management studies.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013004149.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

The role of fractional exhaled nitric oxide in asthma management

Measuring fractional exhaled nitric oxide (FeNO) is a relatively new option for assessing allergic inflammation in the lungs. Clinical management of asthma is challenging, and measuring exhaled nitric oxide can provide another type of data to assist in meeting this challenge. FeNO is easy to perform, and the equipment is not forbiddingly expensive. FeNO provides a complement to traditional measures of asthma control and can help guide diagnostic and treatment choices. This article explains what it is, how the measurements are performed, what the norms are, and its use and limitations in the management of asthma.

Exhaled nitric oxide as screening tool in subjects with suspected asthma without reversibility

BACKGROUND

As fractional exhaled nitric oxide (FeNO) has been evaluated only in certain settings for asthma diagnosis, we investigated whether FeNO values could predict positive methacholine challenge testing (expressed as PD20) in subjects with suspected asthma but without spirometric reversibility.

METHODS

Subjects with asthma-like symptoms and negative bronchodilation test were initially evaluated to undergo FeNO measurement and methacholine bronchial challenge. Diagnostic performance of FeNO to predict PD20 to methacholine <800 μg was examined by constructing receiver-operating characteristic curves.

RESULTS

A total of 112 subjects met the inclusion criteria. In all subjects, FeNO >32 ppb was associated with a sensitivity of 0.47 and a specificity of 0.85 for the identification of the PD20 <800 μg (AUC = 0.691, 95% CI = 0.6-0.775, p = 0.00002). In smokers, FeNO >11 ppb was associated with a sensitivity of 0.85 and a specificity of 0.5 for the identification of PD20 <800 μg (AUC = 0.625, 95% CI = 0.45-0.772, p = 0.18), while in atopics a FeNO level >26 ppb was associated with a sensitivity of 0.55 and a specificity of 0.85 (AUC = 0.677, 95% CI = 0.53-0.8, p = 0.02).

CONCLUSIONS

In subjects with symptoms compatible with asthma but without spirometric reversibility, specific cutoff levels for FeNO levels significantly predict the positive methacholine challenge, with significant confounding factors being atopy and current smoking.

Significance of fractional exhaled nitric oxide combined with serum procalcitonin and C-reactive protein in evaluation of elderly asthma

Bronchial asthma is a common chronic airway inflammatory disease. Asthma is associated with high mortality, especially in the elderly patients. Repeated exacerbations cause disease progression. Therefore, identifying the onset of acute elderly asthma as soon as possible and giving the effective treatment is crucial to improve the prognosis. This study was to investigate the significance of fractional exhaled nitric oxide (FeNO) combined with serum procalcitonin (PCT) and C-reactive protein (CRP) in the evaluation of elderly asthma. A total of 120 elderly patients with an acute attack of asthma from July, 2010 to May, 2012 were studied. On presentation, FeNO, serum PCT and CRP concentrations were measured and sputum culture was also performed. The elderly patients were re-evaluated when they had returned to their stable clinical state. The elderly patients were classified into two groups: positive bacterial culture group (A) and negative bacterial culture group (B). The results showed that: (1) In patients with an acute exacerbation of asthma, 48 (40%) patients had positive sputum bacterial culture and 72 (60%) had negative sputum bacterial culture. (2) The levels of FeNO in patients with acute exacerbation of asthma were significantly higher than in those with no acute exacerbation state (63.8±24.6 vs. 19±6.5 ppb, P<0.05). There was no significant difference in FeNO between group A and group B (P>0.05). (3) The levels of PCT and CRP in group A patients with an acute exacerbation of asthma were significantly higher (P<0.05) than in group B (for PCT: 27.46±9.32 vs. 7.85±3.52 ng/mL; for CRP: 51.25±11.46 vs. 17.11±5.87 mg/L, respectively). When they had returned to stable clinical state, the levels of PCT and CRP in group A were decreased significantly (P<0.05), and those in group B had no significant change (P>0.05) when compared with the exacerbation group. There were no significant differences in the levels of PCT and CRP between the two groups in non-acute exacerbation state (P>0.05). These results suggest that the increase in FeNO indicates the acute exacerbation of asthma, and the elevation of serum PCT and CRP levels may be associated with bacterial infection.